<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
        <li v-for="(item ,index) in arr" :key="index">
               {{ item.name }}    <button @click.prevent="onFn(index)">买书</button>
        </li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr>
        <th>序号</th>
        <th>书名</th>
        <th>单价</th>
        <th>数量</th>
        <th>合计</th>
      </tr>
      <tr v-for="(item ,index) in arr" :key="index">
          <td> {{ index + 1 }} </td>
          <td> {{ item.name }} </td>
          <td> {{ item.price }} </td>
          <td> {{ item.count }} </td>
          <td> {{ item.price * item.count }} </td>
      </tr>
    </table>
    <p>总价格为: {{ sum }} </p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      arr: [
        {
          name: "水浒传",
          price: 107,
          count: 0,
        },
        {
          name: "西游记",
          price: 192,
          count: 0,
        },
        {
          name: "三国演义",
          price: 219,
          count: 0,
        },
        {
          name: "红楼梦",
          price: 178,
          count: 0,
        },
      ],
    };
  },
  methods: {
    onFn(index) {
        this.arr[index].count++
    }
  },
  computed: {
   sum() {
       return this.arr.reduce((prev, item) => prev + (item.price * item.count ), 0)
   },
   
  }
};
</script>

<style scoped>
table{
  text-align: center;
}
</style>